The invention relates to sheet handling apparatus and more particularly to apparatus for aligning and registering sheets moved along a path seriatim to a workstation.
In high-speed reproduction equipment such as electrophotographic copiers, copy sheets are moved seriatim into registration with transferable toner images on a moving transfer member prior to transfer of the toner images to the sheets. A registration mechanism typically intercepts a sheet in advance of the transfer member and either stops it or slows it down in order to synchronize the sheet with an image on the image transfer member. The registration mechanism also effects proper lateral alignment of the copy sheet prior to delivery to the image transfer member by correcting skew in the sheet. Such registration mechanism may take the form of two laterally spaced registration members which are moved into and out of the path of the copy sheet. A misaligned copy sheet striking one of the members will be moved into contact with the other member to properly align the sheet with respect to the image to be transferred. At a preselected time the registration members are moved out of the sheet path and the sheet moved into registration with an image on the transfer member.
One form of registration mechanism is illustrated in commonly assigned U.S. Pat. No. 4,019,733 in which a registration disc is positioned between a pair of continuously driven rollers which contact the disc by means of thrust washers. The registration disc has a registration finger which extends into a sheet path and which is latched to prevent rotation of the disc. A pair of laterally spaced registration discs provide alignment and skew correction. At predetermined time intervals, the registration fingers are unlatched, the discs are rotated with the driven rollers to move the registration fingers out of the sheet feed path, and a copy sheet is fed by the rollers into registration with a toner image on an image transfer member. Although the sheet registration mechanism disclosed in the aforementioned patent has been successfully used for the purpose for which it was intended, difficulties have arisen in adjusting the registration discs with respect to each other. Such adjustments necessitate either movement of the shaft which mounts the nip rollers and registration discs or movement of the latch mechanisms. Adjustments of either the shaft or latch mechanisms are undesirable for several reasons. Movement of the entire nip roller shaft may introduce inaccuracies in timing and alignment of copy sheets fed by the nip rollers which are also mounted on the shaft. It would thus be desirable to be able to correct the alignment of the registration discs without having to also move the sheet feed rollers. Moreover, movement of the latch mechanism may necessitate re-timing of the entire electrographic cycle, a complex and time-consuming task requiring shutdown of the electrographic copier.
Thus, it would be desirable to have the benefits of the simple and efficient design of sheet registration mechanism disclosed in U.S. Pat. No. 4,019,733. It would also be desirable for adjustment of the registration fingers to be effected quickly by a serviceperson without having to tamper with the operation of the sheet feed rollers or of the latching mechanism.